Android
Change System Accent Color auf Android
The system accent color controls the highlight tone used across toggles, sliders, notification shades, app icons and quick settings tiles. By default, Android generates this color automatically from your current wallpaper, which is why switching backgrounds sometimes changes your whole color scheme without warning.
To pick a color manually instead of relying on the wallpaper-based tone, go to Tap on Settings ➔ Tap on Wallpaper & style ➔ Tap on More ➔ Set the System colors and turn on/off the Dark theme. This menu lets you choose a fixed accent tone that stays the same even after you change your wallpaper.
The same screen also holds the switch for the dark theme, since both settings share the color engine. If icons or menus still show the old tone after you save a new color, a quick restart of the launcher or the phone usually forces the interface to redraw with the updated palette.
Some manufacturer skins limit the accent color to a fixed set of swatches instead of a full color wheel, so the exact range of tones can vary between devices even on the same Android version.